Originally posted by sledger I only format when using a card from another camera. Otherwise after the first time, never. Every format shortens the life of the card (somewhat) by the way and in any case, when you format you aren't erasing or treating the entire card capacity, only the FAT (File allocation table) it rewritten.
Just use good quality cards.
Exactly right. When do I reformat? Never, if possible. I've run AV devices with memory cards in many formats (CF, SM, MS, MMC, SD, xD) for about 15 years and I doubt that I've performed 15 reformats total in that time. I can think of maybe 6 times where an in-use card has failed, and I've reformatted in order to 'save' it -- with maybe 3 off-brand cards flunking. With any new card, I do an initial full format and error-check scan. I've flunked maybe 3 cards at that step, and never an SD card.
Why? Because of the life shortening; and because I build a common directory structure on all my cards in each format. And I load a common script onto each card, written to rename and move files to the correct destination on a hard disc. Reformatting destroys that, and it's a minor pain to rebuild it, so I don't reformat.